You are working with a workflow that is created before 4/9 when Matteo added support for both SD1.5 and SDXL.
Solution:
Change the weight_type to “style transfer”, it will automatically distinguish between SD 1.5 and SDXL.
Or test out preloaded new workflows in RunComfy Beta version which has the latest nodes with IPAdapter plus.
For the curious ones, check out this commit to see why it fails. https://github.com/cubiq/ComfyUI_IPAdapter_plus/commit/b334a5c23195ede891ca98995d726b379f46422f